Valve system for internal combustion engine

Abstract

A variable valve system includes a transmission mechanism T which transmits a valve actuating force to an inlet valve 11 and which varies a maximum lift amount of the inlet valve 11 and biasing members 60 . A sub-cam 40 oscillatably supported on a holder 30 driven by a control member 70 has a roller 43 contacting the inlet cam 15 a , a drive cam portion 46 outputting the valve actuating force, and acting portions A contacting the biasing members 60 . The acting portions A are provided in the vicinity of the roller 43 so that biased contact points 45 a 1, 45 b 1 are positioned nearer to a cam contact point 43 a than an oscillation center line Ls and that an acting line L 1 of a biasing force is superposed on the roller 43 as viewed in the direction of the oscillation center line Ls.

1. A variable valve system for an internal combustion engine, comprising:
 a valve cam which actuates an engine valve of the internal combustion engine; 
 a transmission mechanism which transmits a valve actuating force of the valve cam to the engine valve and changes a maximum lift amount of the engine valve by being driven by a control member; and 
 a biasing member which generates a biasing force which brings the transmission mechanism into contact with the valve cam, 
 wherein the transmission mechanism comprises:
 a holder actuated by the control member; and 
 a rocker member oscillatably supported on the holder and disposed in an accommodating space defined by a frame-shaped member of said holder, 
 
 wherein the rocker member comprises:
 a cam contact portion which contacts with the valve cam at a cam contact point; 
 an output portion which outputs the actuating force which is inputted from the valve cam into the cam contact portion, to the engine valve; and 
 an acting portion which contacts with the biasing member at a biased contact portion, and 
 
 wherein the acting portion is provided in the vicinity of the cam contact portion in such a manner that:
 the biased contact point is situated closer to the cam contact point than a rocking center line of the rocker member, and 
 an acting line of the biasing force is superposed on the cam contact portion as viewed from a direction of the rocking center line. 
 
 
     
     
       2. The variable valve system as set forth in  claim 1 ,
 wherein the cam contact portion is a roller which is provided on a support shaft which is provided on an arm portion of the rocker member, and 
 wherein the acting portion is a cylindrical shaft end portion of the support shaft which protrudes to an opposite end to the roller across the arm portion. 
 
     
     
       3. The variable valve system as set forth in  claim 1 ,
 wherein the cam contact portion is a roller which is provided on a support shaft which is provided rotatably on an arm portion of the rocker member, 
 wherein the acting portion is a protruding portion which protrudes from the shaft portion at an opposite end to the roller across the arm portion, and 
 wherein the protruding portion forms an oil reservoir portion for reserving lubricating oil for supply to a sliding portion between the arm portion and the support shaft. 
 
     
     
       4. The variable valve system as set forth in  claim 3 ,
 wherein an axial movement of the support shaft is restricted by a snap ring which is mounted in a mount groove in the arm portion, and 
 wherein the protruding portion is molded integrally with the arm portion where the mount groove is provided. 
 
     
     
       5. The variable valve system as set forth in  claim 1 ,
 wherein the transmission mechanism further comprises:
 a rocker arm which pressurizes the engine valve, said rocker arm being driven by the rocker member and being oscillatably supported on the holder, 
 
 wherein the rocker member further comprises:
 a fulcrum portion which is oscillatably provided on the holder; and 
 a drive cam portion which contacts the rocker arm, 
 
 wherein the holder comprises:
 a pair of arm portions which support the rocker member and which are spaced apart in a direction of an oscillation center line of the rocker member; and 
 a connecting portion which connects together the pair of arm portions, and 
 
 wherein the biasing member is disposed on both sides of the cam contact portion in the direction of the oscillation center line and is held on to the connecting portion. 
 
     
     
       6. The variable valve system as set forth in  claim 5 , wherein the biasing member is disposed in a position where the biasing member is superposed on the drive cam portion in a direction of the acting line of the biasing force. 
     
     
       7. The variable valve system as set forth in  claim 6 ,
 wherein the rocker arm comprises:
 a hydraulic clearance adjusting member for adjusting a valve clearance of the engine valve; and 
 an accommodating portion which accommodates therein the hydraulic clearance adjusting member and which defines an oil chamber in cooperation with the hydraulic clearance adjusting member and 
 
 wherein an air vent hole for discharging air within the oil chamber is provided in the accommodating portion in such a manner as to be directed towards the biasing member. 
 
     
     
       8. The variable valve system as set forth in  claim 7 ,
 wherein the rocker arm comprises a fulcrum portion which is oscillatably supported on the holder, 
 wherein a straight-line oil passage extending towards the fulcrum portion is provided in the rocker arm, said rocker arm having an injection opening in an end portion thereof from which lubricating oil can be injected towards the biasing member, and 
 wherein the biasing member is disposed on an extension of the straight-line oil passage. 
 
     
     
       9. The variable valve system as set forth in  claim 6 ,
 wherein the rocker arm comprises a fulcrum portion which is oscillatably supported on the holder, 
 wherein a straight-line oil passage extending towards the fulcrum portion is provided in the rocker arm, said rocker arm having an injection opening in an end portion thereof from which lubricating oil can be injected towards the biasing member, and 
 wherein the biasing member is disposed on an extension of the straight-line oil passage. 
 
     
     
       10. The variable valve system as set forth in  claim 5 ,
 wherein the rocker arm comprises:
 a hydraulic clearance adjusting member for adjusting a valve clearance of the engine valve; and 
 an accommodating portion which accommodates therein the clearance adjusting member and which defines an oil chamber in cooperation with the clearance adjusting member, and 
 
 wherein an air vent hole for discharging air within the oil chamber is provided in the accommodating portion in such a manner as to be directed towards the biasing member. 
 
     
     
       11. The variable valve system as set forth in  claim 10 ,
 wherein the rocker arm comprises a fulcrum portion which is oscillatably supported on the holder, 
 wherein a straight-line oil passage extending towards the fulcrum portion is provided in the rocker arm, said rocker arm having an injection opening in an end portion thereof from which lubricating oil can be injected towards the biasing member, and 
 wherein the biasing member is disposed on an extension of the straight-line oil passage. 
 
     
     
       12. The variable valve system as set forth in  claim 5 ,
 wherein the rocker arm comprises a fulcrum portion which is oscillatably supported on the holder, 
 wherein a straight-line oil passage extending towards the fulcrum portion is provided in the rocker arm, said rocker arm having an injection opening in an end portion thereof from which lubricating oil can be injected towards the biasing member, and 
 wherein the biasing member is disposed on an extension of the straight-line oil passage. 
 
     
     
       13. The variable valve system as set forth in  claim 5 ,
 wherein the cam contact portion is a roller which is provided on a support shaft which is provided on an arm portion of the rocker member, and 
 wherein the acting portion is a cylindrical shaft end portion of the support shaft which protrudes to an opposite end to the roller across the arm portion. 
 
     
     
       14. The variable valve system as set forth in  claim 1 ,
 wherein the transmission mechanism further comprises:
 a rocker arm which pressurizes the engine valve and which is driven by the rocker member, 
 wherein the holder is supported on an engine main body in such a manner as to be displaced about a displacement center line and oscillatably support the rocker member and the rocker arm, 
 
 wherein the rocker arm is oscillatably supported on an arm portion of the holder, and 
 wherein a distance between an acting point of a control force which is applied to the holder by the control member and an oscillation center line of the rocker arm is made shorter than a distance between the displacement center line and the oscillation center line. 
 
     
     
       15. The variable valve system as set forth in  claim 14 ,
 wherein the control member comprises:
 a control shaft which contacts a first contact portion of the holder so as to apply a driving force thereto; and 
 a controlling biasing member which contacts a second contact portion of the holder and which produces a controlling biasing force for biasing the first contact portion relative to the control shaft, and 
 
 wherein the controlling biasing member contacts the second contact portion in the vicinity of the oscillation center line. 
 
     
     
       16. The variable valve system as set forth in  claim 15 ,
 wherein the support portion is a support shaft provided on the holder, and 
 wherein the first contact portion is a roller which is rotatably supported on the support shaft. 
 
     
     
       17. The variable valve system as set forth in  claim 16 ,
 wherein the rocker arm comprises:
 a plurality of valve pressurizing portions which pressurize a plurality of engine valves; and 
 a pair of fulcrum portions which define an accommodation space which accommodates therein the first contact portion, said pair of fulcrum portions being disposed on both sides of the roller with the roller held therebetween in a direction in which the plurality of valve pressurizing portions are aligned. 
 
 
     
     
       18. The variable valve system as set forth in  claim 15 , wherein a drive cam of the control shaft which contacts the first contact portion, the controlling biasing member and the first contact portion are disposed in positions which intersect a plane which is parallel to a cylinder axis of the internal combustion engine and a rotational center line of the valve cam. 
     
     
       19. The variable valve system as set forth in  claim 14 ,
 wherein the cam contact portion is a roller which is provided on a support shaft which is provided on an arm portion of the rocker member, and 
 wherein the acting portion is a cylindrical shaft end portion of the support shaft which protrudes to an opposite end to the roller across the arm portion. 
 
     
     
       20. The variable valve system as set forth in  claim 1 ,
 wherein the transmission mechanism comprises:
 the rocker member which contacts the valve cam; 
 a rocker arm which pressurizes the engine valve and which is driven by the rocker member; and 
 the holder which is supported on an engine main body in such a manner as to be displaced about a displacement center line and oscillatably support the rocker member and the rocker arm, 
 
 wherein the rocker arm is oscillatably supported on a support portion of the holder, and 
 wherein an acting line of a control force applied to the holder by the control member is superposed on the support portion as viewed from a direction of an oscillation center line of the rocker arm. 
 
     
     
       21. The variable valve system as set forth in  claim 20 ,
 wherein the control member comprises:
 a control shaft which contacts a first contact portion of the holder so as to apply a driving force thereto; and 
 a controlling biasing member which contacts a second contact portion of the holder and which produces a controlling biasing force for biasing the first contact portion relative to the control shaft, and 
 
 wherein the controlling biasing member contacts the second contact portion in the vicinity of the oscillation center line. 
 
     
     
       22. The variable valve system as set forth in  claim 21 ,
 wherein the support portion is a support shaft provided on the holder, and 
 wherein the first contact portion is a roller which is rotatably supported on the support shaft. 
 
     
     
       23. The variable valve system as set forth in  claim 21 , wherein a drive cam of the control shaft which contacts the first contact portion, the controlling biasing member and the first contact portion are disposed in positions which intersect a plane which is parallel to a cylinder axis of the internal combustion engine and a rotational center line of the valve cam. 
     
     
       24. The variable valve system as set forth in  claim 20 ,
 wherein the holder comprises a pair of arm portions on which the support portion is provided, and 
 wherein in the vicinity of the support portion, the controlling biasing member contacts a connecting portion which connects said pair of arm portions together. 
 
     
     
       25. The variable valve system as set forth in  claim 20 ,
 wherein the cam contact portion is a roller which is provided on a support shaft which is provided on an arm portion of the rocker member, and 
 wherein the acting portion is a cylindrical shaft end portion of the support shaft which protrudes to an opposite end to the roller across the arm portion.